The maximum discharge and storage temperature for conventional explosive shells is often limited by the properties of their TNT or TNT-based explosive charge. At sufficiently elevated temperature, this secretes an exudate which may be sucked into capillary gaps in, for example, the thread connection between fuze and shell case. When the temperature once again falls, the exudate crystallizes in the gap to solid form. The high load to which the material in the supporting parts of the shell is exposed during the barrel phase on firing causes minor movements between them. These movements occur as a result of the deformation of the material and, for example, by releasing the pretension of the threads and the tightening of the connection on angular acceleration of the shell. The frictional heat which is generated on movement of the shell parts towards one another is often sufficient to ignite the exudate so that the shell bursts in the barrel. In such instance, the gun will be damaged and the safety of the gun crew put at great jeopardy. In order to avoid this course of events, a maximum firing and storage temperature for the shells is normally adopted, or else the shell is designed with requisite seals about the explosive charge compartment.